Add background Lua workflows, inline child prompts, and layered config

subagents.lua now starts a workflow on its own coroutine and returns a
session-scoped id immediately, so fan-out continues while the primary keeps
working; completion wakes the primary, and later calls read immutable records
from subagents.workflows. Every ctx:agent takes a workflow-unique name so those
records are addressable. A session_start guidance message tells the primary when
to reach for run vs lua.

Children no longer inherit the primary's system context: a child starts from the
fixed child-role instruction plus its profile, and subagents.run/ctx:agent
accept an inline system_prompt instead of a profile. The now-redundant `agent`
form of subagents.models is gone.

Concurrency defaults to five and is configurable through [subagents]
max_concurrent in any layered config.toml; turn boundaries reap only settled
jobs so background workflows survive, while interrupt and session end cancel.

Config roots come from panto.ext.dirs.layers rather than a hand-rolled XDG
lookup, which picks up the base and git-ignored local layers for both agents/
and workflows/.

TOML workflows tighten up: the subagents.workflow tool takes a discovered name
only (inline `steps` duplicated subagents.lua at less power), an optional
top-level `output` array chooses the reported steps and their order instead of
the terminal set, a step with no workflow input gets no empty input heading, and
a workflow naming an undiscovered agent is rejected at discovery rather than
part-way through a run.

1 files changed, 3 insertions, 2 deletions

diff --git a/panto-subagents-0.1.0-1.rockspec b/panto-subagents-0.1.0-1.rockspec
index 693629e..5ae55ff 100644
--- a/panto-subagents-0.1.0-1.rockspec
+++ b/panto-subagents-0.1.0-1.rockspec
@@ -11,8 +11,9 @@
 -- Dependencies. `lyaml` parses profile frontmatter and is a C binding over the
 -- system libyaml, which luarocks does not vendor: a machine without it needs
 -- `brew install libyaml` (or `apt install libyaml-dev`) first, and may need
--- `YAML_DIR=...` passed to luarocks. `toml2lua` (module name `toml`) reads TOML
--- workflows and is pure Lua. `luv` backs the recursive discovery walk and the
+-- `YAML_DIR=...` passed to luarocks. `toml2lua` (module name `toml`) reads the
+-- layered `config.toml` at activation and the TOML workflows afterwards, so it
+-- is required, not optional; it is pure Lua and needs nothing from the system. `luv` backs the recursive discovery walk and the
 -- wake pipes child jobs are polled on, and ships with panto as a pinned
 -- battery, so it is normally already present in the tree this rock installs
 -- into.